1 //===- LiveDebugVariables.cpp - Tracking debug info variables -------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the LiveDebugVariables analysis.
11 //
12 // Remove all DBG_VALUE instructions referencing virtual registers and replace
13 // them with a data structure tracking where live user variables are kept - in a
14 // virtual register or in a stack slot.
15 //
16 // Allow the data structure to be updated during register allocation when values
17 // are moved between registers and stack slots. Finally emit new DBG_VALUE
18 // instructions after register allocation is complete.
19 //
20 //===----------------------------------------------------------------------===//
21
22 #include "LiveDebugVariables.h"
23 #include "llvm/ADT/IntervalMap.h"
24 #include "llvm/ADT/Statistic.h"
25 #include "llvm/CodeGen/LexicalScopes.h"
26 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
27 #include "llvm/CodeGen/MachineDominators.h"
28 #include "llvm/CodeGen/MachineFunction.h"
29 #include "llvm/CodeGen/MachineInstrBuilder.h"
30 #include "llvm/CodeGen/MachineRegisterInfo.h"
31 #include "llvm/CodeGen/Passes.h"
32 #include "llvm/CodeGen/VirtRegMap.h"
33 #include "llvm/IR/Constants.h"
34 #include "llvm/IR/DebugInfo.h"
35 #include "llvm/IR/Metadata.h"
36 #include "llvm/IR/Value.h"
37 #include "llvm/Support/CommandLine.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Target/TargetInstrInfo.h"
40 #include "llvm/Target/TargetMachine.h"
41 #include "llvm/Target/TargetRegisterInfo.h"
42
43 #include <memory>
44
45 using namespace llvm;
46
47 #define DEBUG_TYPE "livedebug"
48
49 static cl::opt<bool>
50 EnableLDV("live-debug-variables", cl::init(true),
51 cl::desc("Enable the live debug variables pass"), cl::Hidden);
52
53 STATISTIC(NumInsertedDebugValues, "Number of DBG_VALUEs inserted");
54 char LiveDebugVariables::ID = 0;
55
56 INITIALIZE_PASS_BEGIN(LiveDebugVariables, "livedebugvars",
57 "Debug Variable Analysis", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)58 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
59 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
60 INITIALIZE_PASS_END(LiveDebugVariables, "livedebugvars",
61 "Debug Variable Analysis", false, false)
62
63 void LiveDebugVariables::getAnalysisUsage(AnalysisUsage &AU) const {
64 AU.addRequired<MachineDominatorTree>();
65 AU.addRequiredTransitive<LiveIntervals>();
66 AU.setPreservesAll();
67 MachineFunctionPass::getAnalysisUsage(AU);
68 }
69
LiveDebugVariables()70 LiveDebugVariables::LiveDebugVariables() : MachineFunctionPass(ID), pImpl(nullptr) {
71 initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
72 }
73
74 /// LocMap - Map of where a user value is live, and its location.
75 typedef IntervalMap<SlotIndex, unsigned, 4> LocMap;
76
77 namespace {
78 /// UserValueScopes - Keeps track of lexical scopes associated with a
79 /// user value's source location.
80 class UserValueScopes {
81 DebugLoc DL;
82 LexicalScopes &LS;
83 SmallPtrSet<const MachineBasicBlock *, 4> LBlocks;
84
85 public:
UserValueScopes(DebugLoc D,LexicalScopes & L)86 UserValueScopes(DebugLoc D, LexicalScopes &L) : DL(D), LS(L) {}
87
88 /// dominates - Return true if current scope dominates at least one machine
89 /// instruction in a given machine basic block.
dominates(MachineBasicBlock * MBB)90 bool dominates(MachineBasicBlock *MBB) {
91 if (LBlocks.empty())
92 LS.getMachineBasicBlocks(DL, LBlocks);
93 if (LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB))
94 return true;
95 return false;
96 }
97 };
98 } // end anonymous namespace
99
100 /// UserValue - A user value is a part of a debug info user variable.
101 ///
102 /// A DBG_VALUE instruction notes that (a sub-register of) a virtual register
103 /// holds part of a user variable. The part is identified by a byte offset.
104 ///
105 /// UserValues are grouped into equivalence classes for easier searching. Two
106 /// user values are related if they refer to the same variable, or if they are
107 /// held by the same virtual register. The equivalence class is the transitive
108 /// closure of that relation.
109 namespace {
110 class LDVImpl;
111 class UserValue {
112 const MDNode *variable; ///< The debug info variable we are part of.
113 unsigned offset; ///< Byte offset into variable.
114 bool IsIndirect; ///< true if this is a register-indirect+offset value.
115 DebugLoc dl; ///< The debug location for the variable. This is
116 ///< used by dwarf writer to find lexical scope.
117 UserValue *leader; ///< Equivalence class leader.
118 UserValue *next; ///< Next value in equivalence class, or null.
119
120 /// Numbered locations referenced by locmap.
121 SmallVector<MachineOperand, 4> locations;
122
123 /// Map of slot indices where this value is live.
124 LocMap locInts;
125
126 /// coalesceLocation - After LocNo was changed, check if it has become
127 /// identical to another location, and coalesce them. This may cause LocNo or
128 /// a later location to be erased, but no earlier location will be erased.
129 void coalesceLocation(unsigned LocNo);
130
131 /// insertDebugValue - Insert a DBG_VALUE into MBB at Idx for LocNo.
132 void insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx, unsigned LocNo,
133 LiveIntervals &LIS, const TargetInstrInfo &TII);
134
135 /// splitLocation - Replace OldLocNo ranges with NewRegs ranges where NewRegs
136 /// is live. Returns true if any changes were made.
137 bool splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
138 LiveIntervals &LIS);
139
140 public:
141 /// UserValue - Create a new UserValue.
UserValue(const MDNode * var,unsigned o,bool i,DebugLoc L,LocMap::Allocator & alloc)142 UserValue(const MDNode *var, unsigned o, bool i, DebugLoc L,
143 LocMap::Allocator &alloc)
144 : variable(var), offset(o), IsIndirect(i), dl(L), leader(this),
145 next(nullptr), locInts(alloc)
146 {}
147
148 /// getLeader - Get the leader of this value's equivalence class.
getLeader()149 UserValue *getLeader() {
150 UserValue *l = leader;
151 while (l != l->leader)
152 l = l->leader;
153 return leader = l;
154 }
155
156 /// getNext - Return the next UserValue in the equivalence class.
getNext() const157 UserValue *getNext() const { return next; }
158
159 /// match - Does this UserValue match the parameters?
match(const MDNode * Var,unsigned Offset,bool indirect) const160 bool match(const MDNode *Var, unsigned Offset, bool indirect) const {
161 return Var == variable && Offset == offset && indirect == IsIndirect;
162 }
163
164 /// merge - Merge equivalence classes.
merge(UserValue * L1,UserValue * L2)165 static UserValue *merge(UserValue *L1, UserValue *L2) {
166 L2 = L2->getLeader();
167 if (!L1)
168 return L2;
169 L1 = L1->getLeader();
170 if (L1 == L2)
171 return L1;
172 // Splice L2 before L1's members.
173 UserValue *End = L2;
174 while (End->next)
175 End->leader = L1, End = End->next;
176 End->leader = L1;
177 End->next = L1->next;
178 L1->next = L2;
179 return L1;
180 }
181
182 /// getLocationNo - Return the location number that matches Loc.
getLocationNo(const MachineOperand & LocMO)183 unsigned getLocationNo(const MachineOperand &LocMO) {
184 if (LocMO.isReg()) {
185 if (LocMO.getReg() == 0)
186 return ~0u;
187 // For register locations we dont care about use/def and other flags.
188 for (unsigned i = 0, e = locations.size(); i != e; ++i)
189 if (locations[i].isReg() &&
190 locations[i].getReg() == LocMO.getReg() &&
191 locations[i].getSubReg() == LocMO.getSubReg())
192 return i;
193 } else
194 for (unsigned i = 0, e = locations.size(); i != e; ++i)
195 if (LocMO.isIdenticalTo(locations[i]))
196 return i;
197 locations.push_back(LocMO);
198 // We are storing a MachineOperand outside a MachineInstr.
199 locations.back().clearParent();
200 // Don't store def operands.
201 if (locations.back().isReg())
202 locations.back().setIsUse();
203 return locations.size() - 1;
204 }
205
206 /// mapVirtRegs - Ensure that all virtual register locations are mapped.
207 void mapVirtRegs(LDVImpl *LDV);
208
209 /// addDef - Add a definition point to this value.
addDef(SlotIndex Idx,const MachineOperand & LocMO)210 void addDef(SlotIndex Idx, const MachineOperand &LocMO) {
211 // Add a singular (Idx,Idx) -> Loc mapping.
212 LocMap::iterator I = locInts.find(Idx);
213 if (!I.valid() || I.start() != Idx)
214 I.insert(Idx, Idx.getNextSlot(), getLocationNo(LocMO));
215 else
216 // A later DBG_VALUE at the same SlotIndex overrides the old location.
217 I.setValue(getLocationNo(LocMO));
218 }
219
220 /// extendDef - Extend the current definition as far as possible down the
221 /// dominator tree. Stop when meeting an existing def or when leaving the live
222 /// range of VNI.
223 /// End points where VNI is no longer live are added to Kills.
224 /// @param Idx Starting point for the definition.
225 /// @param LocNo Location number to propagate.
226 /// @param LR Restrict liveness to where LR has the value VNI. May be null.
227 /// @param VNI When LR is not null, this is the value to restrict to.
228 /// @param Kills Append end points of VNI's live range to Kills.
229 /// @param LIS Live intervals analysis.
230 /// @param MDT Dominator tree.
231 void extendDef(SlotIndex Idx, unsigned LocNo,
232 LiveRange *LR, const VNInfo *VNI,
233 SmallVectorImpl<SlotIndex> *Kills,
234 LiveIntervals &LIS, MachineDominatorTree &MDT,
235 UserValueScopes &UVS);
236
237 /// addDefsFromCopies - The value in LI/LocNo may be copies to other
238 /// registers. Determine if any of the copies are available at the kill
239 /// points, and add defs if possible.
240 /// @param LI Scan for copies of the value in LI->reg.
241 /// @param LocNo Location number of LI->reg.
242 /// @param Kills Points where the range of LocNo could be extended.
243 /// @param NewDefs Append (Idx, LocNo) of inserted defs here.
244 void addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
245 const SmallVectorImpl<SlotIndex> &Kills,
246 SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
247 MachineRegisterInfo &MRI,
248 LiveIntervals &LIS);
249
250 /// computeIntervals - Compute the live intervals of all locations after
251 /// collecting all their def points.
252 void computeIntervals(MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
253 LiveIntervals &LIS, MachineDominatorTree &MDT,
254 UserValueScopes &UVS);
255
256 /// splitRegister - Replace OldReg ranges with NewRegs ranges where NewRegs is
257 /// live. Returns true if any changes were made.
258 bool splitRegister(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
259 LiveIntervals &LIS);
260
261 /// rewriteLocations - Rewrite virtual register locations according to the
262 /// provided virtual register map.
263 void rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI);
264
265 /// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
266 void emitDebugValues(VirtRegMap *VRM,
267 LiveIntervals &LIS, const TargetInstrInfo &TRI);
268
269 /// findDebugLoc - Return DebugLoc used for this DBG_VALUE instruction. A
270 /// variable may have more than one corresponding DBG_VALUE instructions.
271 /// Only first one needs DebugLoc to identify variable's lexical scope
272 /// in source file.
273 DebugLoc findDebugLoc();
274
275 /// getDebugLoc - Return DebugLoc of this UserValue.
getDebugLoc()276 DebugLoc getDebugLoc() { return dl;}
277 void print(raw_ostream&, const TargetMachine*);
278 };
279 } // namespace
280
281 /// LDVImpl - Implementation of the LiveDebugVariables pass.
282 namespace {
283 class LDVImpl {
284 LiveDebugVariables &pass;
285 LocMap::Allocator allocator;
286 MachineFunction *MF;
287 LiveIntervals *LIS;
288 LexicalScopes LS;
289 MachineDominatorTree *MDT;
290 const TargetRegisterInfo *TRI;
291
292 /// Whether emitDebugValues is called.
293 bool EmitDone;
294 /// Whether the machine function is modified during the pass.
295 bool ModifiedMF;
296
297 /// userValues - All allocated UserValue instances.
298 SmallVector<std::unique_ptr<UserValue>, 8> userValues;
299
300 /// Map virtual register to eq class leader.
301 typedef DenseMap<unsigned, UserValue*> VRMap;
302 VRMap virtRegToEqClass;
303
304 /// Map user variable to eq class leader.
305 typedef DenseMap<const MDNode *, UserValue*> UVMap;
306 UVMap userVarMap;
307
308 /// getUserValue - Find or create a UserValue.
309 UserValue *getUserValue(const MDNode *Var, unsigned Offset,
310 bool IsIndirect, DebugLoc DL);
311
312 /// lookupVirtReg - Find the EC leader for VirtReg or null.
313 UserValue *lookupVirtReg(unsigned VirtReg);
314
315 /// handleDebugValue - Add DBG_VALUE instruction to our maps.
316 /// @param MI DBG_VALUE instruction
317 /// @param Idx Last valid SLotIndex before instruction.
318 /// @return True if the DBG_VALUE instruction should be deleted.
319 bool handleDebugValue(MachineInstr *MI, SlotIndex Idx);
320
321 /// collectDebugValues - Collect and erase all DBG_VALUE instructions, adding
322 /// a UserValue def for each instruction.
323 /// @param mf MachineFunction to be scanned.
324 /// @return True if any debug values were found.
325 bool collectDebugValues(MachineFunction &mf);
326
327 /// computeIntervals - Compute the live intervals of all user values after
328 /// collecting all their def points.
329 void computeIntervals();
330
331 public:
LDVImpl(LiveDebugVariables * ps)332 LDVImpl(LiveDebugVariables *ps)
333 : pass(*ps), MF(nullptr), EmitDone(false), ModifiedMF(false) {}
334 bool runOnMachineFunction(MachineFunction &mf);
335
336 /// clear - Release all memory.
clear()337 void clear() {
338 MF = nullptr;
339 userValues.clear();
340 virtRegToEqClass.clear();
341 userVarMap.clear();
342 // Make sure we call emitDebugValues if the machine function was modified.
343 assert((!ModifiedMF || EmitDone) &&
344 "Dbg values are not emitted in LDV");
345 EmitDone = false;
346 ModifiedMF = false;
347 }
348
349 /// mapVirtReg - Map virtual register to an equivalence class.
350 void mapVirtReg(unsigned VirtReg, UserValue *EC);
351
352 /// splitRegister - Replace all references to OldReg with NewRegs.
353 void splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs);
354
355 /// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
356 void emitDebugValues(VirtRegMap *VRM);
357
358 void print(raw_ostream&);
359 };
360 } // namespace
361
print(raw_ostream & OS,const TargetMachine * TM)362 void UserValue::print(raw_ostream &OS, const TargetMachine *TM) {
363 DIVariable DV(variable);
364 OS << "!\"";
365 DV.printExtendedName(OS);
366 OS << "\"\t";
367 if (offset)
368 OS << '+' << offset;
369 for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
370 OS << " [" << I.start() << ';' << I.stop() << "):";
371 if (I.value() == ~0u)
372 OS << "undef";
373 else
374 OS << I.value();
375 }
376 for (unsigned i = 0, e = locations.size(); i != e; ++i) {
377 OS << " Loc" << i << '=';
378 locations[i].print(OS, TM);
379 }
380 OS << '\n';
381 }
382
print(raw_ostream & OS)383 void LDVImpl::print(raw_ostream &OS) {
384 OS << "********** DEBUG VARIABLES **********\n";
385 for (unsigned i = 0, e = userValues.size(); i != e; ++i)
386 userValues[i]->print(OS, &MF->getTarget());
387 }
388
coalesceLocation(unsigned LocNo)389 void UserValue::coalesceLocation(unsigned LocNo) {
390 unsigned KeepLoc = 0;
391 for (unsigned e = locations.size(); KeepLoc != e; ++KeepLoc) {
392 if (KeepLoc == LocNo)
393 continue;
394 if (locations[KeepLoc].isIdenticalTo(locations[LocNo]))
395 break;
396 }
397 // No matches.
398 if (KeepLoc == locations.size())
399 return;
400
401 // Keep the smaller location, erase the larger one.
402 unsigned EraseLoc = LocNo;
403 if (KeepLoc > EraseLoc)
404 std::swap(KeepLoc, EraseLoc);
405 locations.erase(locations.begin() + EraseLoc);
406
407 // Rewrite values.
408 for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
409 unsigned v = I.value();
410 if (v == EraseLoc)
411 I.setValue(KeepLoc); // Coalesce when possible.
412 else if (v > EraseLoc)
413 I.setValueUnchecked(v-1); // Avoid coalescing with untransformed values.
414 }
415 }
416
mapVirtRegs(LDVImpl * LDV)417 void UserValue::mapVirtRegs(LDVImpl *LDV) {
418 for (unsigned i = 0, e = locations.size(); i != e; ++i)
419 if (locations[i].isReg() &&
420 TargetRegisterInfo::isVirtualRegister(locations[i].getReg()))
421 LDV->mapVirtReg(locations[i].getReg(), this);
422 }
423
getUserValue(const MDNode * Var,unsigned Offset,bool IsIndirect,DebugLoc DL)424 UserValue *LDVImpl::getUserValue(const MDNode *Var, unsigned Offset,
425 bool IsIndirect, DebugLoc DL) {
426 UserValue *&Leader = userVarMap[Var];
427 if (Leader) {
428 UserValue *UV = Leader->getLeader();
429 Leader = UV;
430 for (; UV; UV = UV->getNext())
431 if (UV->match(Var, Offset, IsIndirect))
432 return UV;
433 }
434
435 userValues.push_back(
436 make_unique<UserValue>(Var, Offset, IsIndirect, DL, allocator));
437 UserValue *UV = userValues.back().get();
438 Leader = UserValue::merge(Leader, UV);
439 return UV;
440 }
441
mapVirtReg(unsigned VirtReg,UserValue * EC)442 void LDVImpl::mapVirtReg(unsigned VirtReg, UserValue *EC) {
443 assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && "Only map VirtRegs");
444 UserValue *&Leader = virtRegToEqClass[VirtReg];
445 Leader = UserValue::merge(Leader, EC);
446 }
447
lookupVirtReg(unsigned VirtReg)448 UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
449 if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
450 return UV->getLeader();
451 return nullptr;
452 }
453
handleDebugValue(MachineInstr * MI,SlotIndex Idx)454 bool LDVImpl::handleDebugValue(MachineInstr *MI, SlotIndex Idx) {
455 // DBG_VALUE loc, offset, variable
456 if (MI->getNumOperands() != 3 ||
457 !(MI->getOperand(1).isReg() || MI->getOperand(1).isImm()) ||
458 !MI->getOperand(2).isMetadata()) {
459 DEBUG(dbgs() << "Can't handle " << *MI);
460 return false;
461 }
462
463 // Get or create the UserValue for (variable,offset).
464 bool IsIndirect = MI->isIndirectDebugValue();
465 unsigned Offset = IsIndirect ? MI->getOperand(1).getImm() : 0;
466 const MDNode *Var = MI->getOperand(2).getMetadata();
467 //here.
468 UserValue *UV = getUserValue(Var, Offset, IsIndirect, MI->getDebugLoc());
469 UV->addDef(Idx, MI->getOperand(0));
470 return true;
471 }
472
collectDebugValues(MachineFunction & mf)473 bool LDVImpl::collectDebugValues(MachineFunction &mf) {
474 bool Changed = false;
475 for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
476 ++MFI) {
477 MachineBasicBlock *MBB = MFI;
478 for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
479 MBBI != MBBE;) {
480 if (!MBBI->isDebugValue()) {
481 ++MBBI;
482 continue;
483 }
484 // DBG_VALUE has no slot index, use the previous instruction instead.
485 SlotIndex Idx = MBBI == MBB->begin() ?
486 LIS->getMBBStartIdx(MBB) :
487 LIS->getInstructionIndex(std::prev(MBBI)).getRegSlot();
488 // Handle consecutive DBG_VALUE instructions with the same slot index.
489 do {
490 if (handleDebugValue(MBBI, Idx)) {
491 MBBI = MBB->erase(MBBI);
492 Changed = true;
493 } else
494 ++MBBI;
495 } while (MBBI != MBBE && MBBI->isDebugValue());
496 }
497 }
498 return Changed;
499 }
500
extendDef(SlotIndex Idx,unsigned LocNo,LiveRange * LR,const VNInfo * VNI,SmallVectorImpl<SlotIndex> * Kills,LiveIntervals & LIS,MachineDominatorTree & MDT,UserValueScopes & UVS)501 void UserValue::extendDef(SlotIndex Idx, unsigned LocNo,
502 LiveRange *LR, const VNInfo *VNI,
503 SmallVectorImpl<SlotIndex> *Kills,
504 LiveIntervals &LIS, MachineDominatorTree &MDT,
505 UserValueScopes &UVS) {
506 SmallVector<SlotIndex, 16> Todo;
507 Todo.push_back(Idx);
508 do {
509 SlotIndex Start = Todo.pop_back_val();
510 MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
511 SlotIndex Stop = LIS.getMBBEndIdx(MBB);
512 LocMap::iterator I = locInts.find(Start);
513
514 // Limit to VNI's live range.
515 bool ToEnd = true;
516 if (LR && VNI) {
517 LiveInterval::Segment *Segment = LR->getSegmentContaining(Start);
518 if (!Segment || Segment->valno != VNI) {
519 if (Kills)
520 Kills->push_back(Start);
521 continue;
522 }
523 if (Segment->end < Stop)
524 Stop = Segment->end, ToEnd = false;
525 }
526
527 // There could already be a short def at Start.
528 if (I.valid() && I.start() <= Start) {
529 // Stop when meeting a different location or an already extended interval.
530 Start = Start.getNextSlot();
531 if (I.value() != LocNo || I.stop() != Start)
532 continue;
533 // This is a one-slot placeholder. Just skip it.
534 ++I;
535 }
536
537 // Limited by the next def.
538 if (I.valid() && I.start() < Stop)
539 Stop = I.start(), ToEnd = false;
540 // Limited by VNI's live range.
541 else if (!ToEnd && Kills)
542 Kills->push_back(Stop);
543
544 if (Start >= Stop)
545 continue;
546
547 I.insert(Start, Stop, LocNo);
548
549 // If we extended to the MBB end, propagate down the dominator tree.
550 if (!ToEnd)
551 continue;
552 const std::vector<MachineDomTreeNode*> &Children =
553 MDT.getNode(MBB)->getChildren();
554 for (unsigned i = 0, e = Children.size(); i != e; ++i) {
555 MachineBasicBlock *MBB = Children[i]->getBlock();
556 if (UVS.dominates(MBB))
557 Todo.push_back(LIS.getMBBStartIdx(MBB));
558 }
559 } while (!Todo.empty());
560 }
561
562 void
addDefsFromCopies(LiveInterval * LI,unsigned LocNo,const SmallVectorImpl<SlotIndex> & Kills,SmallVectorImpl<std::pair<SlotIndex,unsigned>> & NewDefs,MachineRegisterInfo & MRI,LiveIntervals & LIS)563 UserValue::addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
564 const SmallVectorImpl<SlotIndex> &Kills,
565 SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
566 MachineRegisterInfo &MRI, LiveIntervals &LIS) {
567 if (Kills.empty())
568 return;
569 // Don't track copies from physregs, there are too many uses.
570 if (!TargetRegisterInfo::isVirtualRegister(LI->reg))
571 return;
572
573 // Collect all the (vreg, valno) pairs that are copies of LI.
574 SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
575 for (MachineOperand &MO : MRI.use_nodbg_operands(LI->reg)) {
576 MachineInstr *MI = MO.getParent();
577 // Copies of the full value.
578 if (MO.getSubReg() || !MI->isCopy())
579 continue;
580 unsigned DstReg = MI->getOperand(0).getReg();
581
582 // Don't follow copies to physregs. These are usually setting up call
583 // arguments, and the argument registers are always call clobbered. We are
584 // better off in the source register which could be a callee-saved register,
585 // or it could be spilled.
586 if (!TargetRegisterInfo::isVirtualRegister(DstReg))
587 continue;
588
589 // Is LocNo extended to reach this copy? If not, another def may be blocking
590 // it, or we are looking at a wrong value of LI.
591 SlotIndex Idx = LIS.getInstructionIndex(MI);
592 LocMap::iterator I = locInts.find(Idx.getRegSlot(true));
593 if (!I.valid() || I.value() != LocNo)
594 continue;
595
596 if (!LIS.hasInterval(DstReg))
597 continue;
598 LiveInterval *DstLI = &LIS.getInterval(DstReg);
599 const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getRegSlot());
600 assert(DstVNI && DstVNI->def == Idx.getRegSlot() && "Bad copy value");
601 CopyValues.push_back(std::make_pair(DstLI, DstVNI));
602 }
603
604 if (CopyValues.empty())
605 return;
606
607 DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI << '\n');
608
609 // Try to add defs of the copied values for each kill point.
610 for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
611 SlotIndex Idx = Kills[i];
612 for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
613 LiveInterval *DstLI = CopyValues[j].first;
614 const VNInfo *DstVNI = CopyValues[j].second;
615 if (DstLI->getVNInfoAt(Idx) != DstVNI)
616 continue;
617 // Check that there isn't already a def at Idx
618 LocMap::iterator I = locInts.find(Idx);
619 if (I.valid() && I.start() <= Idx)
620 continue;
621 DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
622 << DstVNI->id << " in " << *DstLI << '\n');
623 MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
624 assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
625 unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
626 I.insert(Idx, Idx.getNextSlot(), LocNo);
627 NewDefs.push_back(std::make_pair(Idx, LocNo));
628 break;
629 }
630 }
631 }
632
633 void
computeIntervals(MachineRegisterInfo & MRI,const TargetRegisterInfo & TRI,LiveIntervals & LIS,MachineDominatorTree & MDT,UserValueScopes & UVS)634 UserValue::computeIntervals(MachineRegisterInfo &MRI,
635 const TargetRegisterInfo &TRI,
636 LiveIntervals &LIS,
637 MachineDominatorTree &MDT,
638 UserValueScopes &UVS) {
639 SmallVector<std::pair<SlotIndex, unsigned>, 16> Defs;
640
641 // Collect all defs to be extended (Skipping undefs).
642 for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
643 if (I.value() != ~0u)
644 Defs.push_back(std::make_pair(I.start(), I.value()));
645
646 // Extend all defs, and possibly add new ones along the way.
647 for (unsigned i = 0; i != Defs.size(); ++i) {
648 SlotIndex Idx = Defs[i].first;
649 unsigned LocNo = Defs[i].second;
650 const MachineOperand &Loc = locations[LocNo];
651
652 if (!Loc.isReg()) {
653 extendDef(Idx, LocNo, nullptr, nullptr, nullptr, LIS, MDT, UVS);
654 continue;
655 }
656
657 // Register locations are constrained to where the register value is live.
658 if (TargetRegisterInfo::isVirtualRegister(Loc.getReg())) {
659 LiveInterval *LI = nullptr;
660 const VNInfo *VNI = nullptr;
661 if (LIS.hasInterval(Loc.getReg())) {
662 LI = &LIS.getInterval(Loc.getReg());
663 VNI = LI->getVNInfoAt(Idx);
664 }
665 SmallVector<SlotIndex, 16> Kills;
666 extendDef(Idx, LocNo, LI, VNI, &Kills, LIS, MDT, UVS);
667 if (LI)
668 addDefsFromCopies(LI, LocNo, Kills, Defs, MRI, LIS);
669 continue;
670 }
671
672 // For physregs, use the live range of the first regunit as a guide.
673 unsigned Unit = *MCRegUnitIterator(Loc.getReg(), &TRI);
674 LiveRange *LR = &LIS.getRegUnit(Unit);
675 const VNInfo *VNI = LR->getVNInfoAt(Idx);
676 // Don't track copies from physregs, it is too expensive.
677 extendDef(Idx, LocNo, LR, VNI, nullptr, LIS, MDT, UVS);
678 }
679
680 // Finally, erase all the undefs.
681 for (LocMap::iterator I = locInts.begin(); I.valid();)
682 if (I.value() == ~0u)
683 I.erase();
684 else
685 ++I;
686 }
687
computeIntervals()688 void LDVImpl::computeIntervals() {
689 for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
690 UserValueScopes UVS(userValues[i]->getDebugLoc(), LS);
691 userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS, *MDT, UVS);
692 userValues[i]->mapVirtRegs(this);
693 }
694 }
695
runOnMachineFunction(MachineFunction & mf)696 bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
697 clear();
698 MF = &mf;
699 LIS = &pass.getAnalysis<LiveIntervals>();
700 MDT = &pass.getAnalysis<MachineDominatorTree>();
701 TRI = mf.getTarget().getRegisterInfo();
702 LS.initialize(mf);
703 DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
704 << mf.getName() << " **********\n");
705
706 bool Changed = collectDebugValues(mf);
707 computeIntervals();
708 DEBUG(print(dbgs()));
709 ModifiedMF = Changed;
710 return Changed;
711 }
712
runOnMachineFunction(MachineFunction & mf)713 bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
714 if (!EnableLDV)
715 return false;
716 if (!FunctionDIs.count(mf.getFunction()))
717 return false;
718 if (!pImpl)
719 pImpl = new LDVImpl(this);
720 return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
721 }
722
releaseMemory()723 void LiveDebugVariables::releaseMemory() {
724 if (pImpl)
725 static_cast<LDVImpl*>(pImpl)->clear();
726 }
727
~LiveDebugVariables()728 LiveDebugVariables::~LiveDebugVariables() {
729 if (pImpl)
730 delete static_cast<LDVImpl*>(pImpl);
731 }
732
733 //===----------------------------------------------------------------------===//
734 // Live Range Splitting
735 //===----------------------------------------------------------------------===//
736
737 bool
splitLocation(unsigned OldLocNo,ArrayRef<unsigned> NewRegs,LiveIntervals & LIS)738 UserValue::splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
739 LiveIntervals& LIS) {
740 DEBUG({
741 dbgs() << "Splitting Loc" << OldLocNo << '\t';
742 print(dbgs(), nullptr);
743 });
744 bool DidChange = false;
745 LocMap::iterator LocMapI;
746 LocMapI.setMap(locInts);
747 for (unsigned i = 0; i != NewRegs.size(); ++i) {
748 LiveInterval *LI = &LIS.getInterval(NewRegs[i]);
749 if (LI->empty())
750 continue;
751
752 // Don't allocate the new LocNo until it is needed.
753 unsigned NewLocNo = ~0u;
754
755 // Iterate over the overlaps between locInts and LI.
756 LocMapI.find(LI->beginIndex());
757 if (!LocMapI.valid())
758 continue;
759 LiveInterval::iterator LII = LI->advanceTo(LI->begin(), LocMapI.start());
760 LiveInterval::iterator LIE = LI->end();
761 while (LocMapI.valid() && LII != LIE) {
762 // At this point, we know that LocMapI.stop() > LII->start.
763 LII = LI->advanceTo(LII, LocMapI.start());
764 if (LII == LIE)
765 break;
766
767 // Now LII->end > LocMapI.start(). Do we have an overlap?
768 if (LocMapI.value() == OldLocNo && LII->start < LocMapI.stop()) {
769 // Overlapping correct location. Allocate NewLocNo now.
770 if (NewLocNo == ~0u) {
771 MachineOperand MO = MachineOperand::CreateReg(LI->reg, false);
772 MO.setSubReg(locations[OldLocNo].getSubReg());
773 NewLocNo = getLocationNo(MO);
774 DidChange = true;
775 }
776
777 SlotIndex LStart = LocMapI.start();
778 SlotIndex LStop = LocMapI.stop();
779
780 // Trim LocMapI down to the LII overlap.
781 if (LStart < LII->start)
782 LocMapI.setStartUnchecked(LII->start);
783 if (LStop > LII->end)
784 LocMapI.setStopUnchecked(LII->end);
785
786 // Change the value in the overlap. This may trigger coalescing.
787 LocMapI.setValue(NewLocNo);
788
789 // Re-insert any removed OldLocNo ranges.
790 if (LStart < LocMapI.start()) {
791 LocMapI.insert(LStart, LocMapI.start(), OldLocNo);
792 ++LocMapI;
793 assert(LocMapI.valid() && "Unexpected coalescing");
794 }
795 if (LStop > LocMapI.stop()) {
796 ++LocMapI;
797 LocMapI.insert(LII->end, LStop, OldLocNo);
798 --LocMapI;
799 }
800 }
801
802 // Advance to the next overlap.
803 if (LII->end < LocMapI.stop()) {
804 if (++LII == LIE)
805 break;
806 LocMapI.advanceTo(LII->start);
807 } else {
808 ++LocMapI;
809 if (!LocMapI.valid())
810 break;
811 LII = LI->advanceTo(LII, LocMapI.start());
812 }
813 }
814 }
815
816 // Finally, remove any remaining OldLocNo intervals and OldLocNo itself.
817 locations.erase(locations.begin() + OldLocNo);
818 LocMapI.goToBegin();
819 while (LocMapI.valid()) {
820 unsigned v = LocMapI.value();
821 if (v == OldLocNo) {
822 DEBUG(dbgs() << "Erasing [" << LocMapI.start() << ';'
823 << LocMapI.stop() << ")\n");
824 LocMapI.erase();
825 } else {
826 if (v > OldLocNo)
827 LocMapI.setValueUnchecked(v-1);
828 ++LocMapI;
829 }
830 }
831
832 DEBUG({dbgs() << "Split result: \t"; print(dbgs(), nullptr);});
833 return DidChange;
834 }
835
836 bool
splitRegister(unsigned OldReg,ArrayRef<unsigned> NewRegs,LiveIntervals & LIS)837 UserValue::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs,
838 LiveIntervals &LIS) {
839 bool DidChange = false;
840 // Split locations referring to OldReg. Iterate backwards so splitLocation can
841 // safely erase unused locations.
842 for (unsigned i = locations.size(); i ; --i) {
843 unsigned LocNo = i-1;
844 const MachineOperand *Loc = &locations[LocNo];
845 if (!Loc->isReg() || Loc->getReg() != OldReg)
846 continue;
847 DidChange |= splitLocation(LocNo, NewRegs, LIS);
848 }
849 return DidChange;
850 }
851
splitRegister(unsigned OldReg,ArrayRef<unsigned> NewRegs)852 void LDVImpl::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs) {
853 bool DidChange = false;
854 for (UserValue *UV = lookupVirtReg(OldReg); UV; UV = UV->getNext())
855 DidChange |= UV->splitRegister(OldReg, NewRegs, *LIS);
856
857 if (!DidChange)
858 return;
859
860 // Map all of the new virtual registers.
861 UserValue *UV = lookupVirtReg(OldReg);
862 for (unsigned i = 0; i != NewRegs.size(); ++i)
863 mapVirtReg(NewRegs[i], UV);
864 }
865
866 void LiveDebugVariables::
splitRegister(unsigned OldReg,ArrayRef<unsigned> NewRegs,LiveIntervals & LIS)867 splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs, LiveIntervals &LIS) {
868 if (pImpl)
869 static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
870 }
871
872 void
rewriteLocations(VirtRegMap & VRM,const TargetRegisterInfo & TRI)873 UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI) {
874 // Iterate over locations in reverse makes it easier to handle coalescing.
875 for (unsigned i = locations.size(); i ; --i) {
876 unsigned LocNo = i-1;
877 MachineOperand &Loc = locations[LocNo];
878 // Only virtual registers are rewritten.
879 if (!Loc.isReg() || !Loc.getReg() ||
880 !TargetRegisterInfo::isVirtualRegister(Loc.getReg()))
881 continue;
882 unsigned VirtReg = Loc.getReg();
883 if (VRM.isAssignedReg(VirtReg) &&
884 TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
885 // This can create a %noreg operand in rare cases when the sub-register
886 // index is no longer available. That means the user value is in a
887 // non-existent sub-register, and %noreg is exactly what we want.
888 Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
889 } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT) {
890 // FIXME: Translate SubIdx to a stackslot offset.
891 Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
892 } else {
893 Loc.setReg(0);
894 Loc.setSubReg(0);
895 }
896 coalesceLocation(LocNo);
897 }
898 }
899
900 /// findInsertLocation - Find an iterator for inserting a DBG_VALUE
901 /// instruction.
902 static MachineBasicBlock::iterator
findInsertLocation(MachineBasicBlock * MBB,SlotIndex Idx,LiveIntervals & LIS)903 findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
904 LiveIntervals &LIS) {
905 SlotIndex Start = LIS.getMBBStartIdx(MBB);
906 Idx = Idx.getBaseIndex();
907
908 // Try to find an insert location by going backwards from Idx.
909 MachineInstr *MI;
910 while (!(MI = LIS.getInstructionFromIndex(Idx))) {
911 // We've reached the beginning of MBB.
912 if (Idx == Start) {
913 MachineBasicBlock::iterator I = MBB->SkipPHIsAndLabels(MBB->begin());
914 return I;
915 }
916 Idx = Idx.getPrevIndex();
917 }
918
919 // Don't insert anything after the first terminator, though.
920 return MI->isTerminator() ? MBB->getFirstTerminator() :
921 std::next(MachineBasicBlock::iterator(MI));
922 }
923
findDebugLoc()924 DebugLoc UserValue::findDebugLoc() {
925 DebugLoc D = dl;
926 dl = DebugLoc();
927 return D;
928 }
insertDebugValue(MachineBasicBlock * MBB,SlotIndex Idx,unsigned LocNo,LiveIntervals & LIS,const TargetInstrInfo & TII)929 void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
930 unsigned LocNo,
931 LiveIntervals &LIS,
932 const TargetInstrInfo &TII) {
933 MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
934 MachineOperand &Loc = locations[LocNo];
935 ++NumInsertedDebugValues;
936
937 if (Loc.isReg())
938 BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
939 IsIndirect, Loc.getReg(), offset, variable);
940 else
941 BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
942 .addOperand(Loc).addImm(offset).addMetadata(variable);
943 }
944
emitDebugValues(VirtRegMap * VRM,LiveIntervals & LIS,const TargetInstrInfo & TII)945 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
946 const TargetInstrInfo &TII) {
947 MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
948
949 for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
950 SlotIndex Start = I.start();
951 SlotIndex Stop = I.stop();
952 unsigned LocNo = I.value();
953 DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << LocNo);
954 MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start);
955 SlotIndex MBBEnd = LIS.getMBBEndIdx(MBB);
956
957 DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
958 insertDebugValue(MBB, Start, LocNo, LIS, TII);
959 // This interval may span multiple basic blocks.
960 // Insert a DBG_VALUE into each one.
961 while(Stop > MBBEnd) {
962 // Move to the next block.
963 Start = MBBEnd;
964 if (++MBB == MFEnd)
965 break;
966 MBBEnd = LIS.getMBBEndIdx(MBB);
967 DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
968 insertDebugValue(MBB, Start, LocNo, LIS, TII);
969 }
970 DEBUG(dbgs() << '\n');
971 if (MBB == MFEnd)
972 break;
973
974 ++I;
975 }
976 }
977
emitDebugValues(VirtRegMap * VRM)978 void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
979 DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
980 if (!MF)
981 return;
982 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
983 for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
984 DEBUG(userValues[i]->print(dbgs(), &MF->getTarget()));
985 userValues[i]->rewriteLocations(*VRM, *TRI);
986 userValues[i]->emitDebugValues(VRM, *LIS, *TII);
987 }
988 EmitDone = true;
989 }
990
emitDebugValues(VirtRegMap * VRM)991 void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
992 if (pImpl)
993 static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
994 }
995
doInitialization(Module & M)996 bool LiveDebugVariables::doInitialization(Module &M) {
997 FunctionDIs = makeSubprogramMap(M);
998 return Pass::doInitialization(M);
999 }
1000
1001 #ifndef NDEBUG
dump()1002 void LiveDebugVariables::dump() {
1003 if (pImpl)
1004 static_cast<LDVImpl*>(pImpl)->print(dbgs());
1005 }
1006 #endif
1007